Sorry, disagree. (Get ready for a single anecdote.) As a child I had a German Shepherd who had an accidental litter (as a 2yo, so it's not as if she was "too old to care"). While we cared for the pups my parents made sure we knew to respect the mother-guardian mentality.
Always good advice, regardless.
However, never once did she show any serious threat, maybe minor, nor EVER automatically launch into an attack on anyone, me or even friends.
My aunt has had many Border Collie litters without "no-warning" attacks - never mind horrid injuries.
And I otherwise don't hear too much about breeders or casual BYB having real problems with their bitches.
This dog sounds as if she just automatically jumped the girl, far from the litter, without warning. Then, typical, held on for dear life. That wouldn't surprise me too much with the pit-bull type. Over-sensitivity, in this case; high drive you might call it. Most dogs, when "disciplining", will simply snap at one - maybe even actually bite - but let go; that's the "last warning". And that's usually after a warning "growl" that's ignored.
I wonder if the dog it ate the girl's lip and chin because it protecting puppies?